This invention relates generally to the mounting of electronic components and is particularly directed to the mounting of a toroidal coil and ferrite core assembly on a printed wiring board (PWB).
In many electronic circuits, a conducting coil is wound around a doughnut-shaped core for providing the circuit with a desired inductance. The core possesses high magnetic permeability and is typically comprised of a ferrite or ceramic material. The ends of the coil are coupled such as by soldering to respective conductors on a PWB upon which the toroidal coil and core combination is mounted.
Because space is at a premium on the PWB, the toroidal coil/core combination is generally mounted in an upright position using any one of several well known mounting arrangements. For example, FIG. 1 illustrates the combination of a toroidal coil 10 and core 12 mounted to a PWB 14 by means of the combination of glue, or epoxy cement, and a curved mounting base 18. In mounting the toroidal coil and core combination on the PWB 14, a glue applicator 22 is used to apply various glue portions 20a, 20b and 20c to the PWB 14, the mounting base 18, and the toroidal coil/core combination. In this manner, the toroidal coil/core combination is affixed to an upper portion of the mounting base 18 which, in turn, is attached to one surface of the PWB 14. Each of the ends 16 of the toroidal coil 10 typically extend through respective apertures in the PWB 14 and are coupled such as by soldering to circuitry (not shown) on the PWB.
Another prior art approach, as shown in FIG. 2, makes use of one or more threaded mounting pins 38 inserted through an aperture in the PWB 33 for securely engaging a contoured mounting base 34 and maintaining it in position on the PWB. Glue or epoxy cementt 36 is positioned on the upper, concave surface of the mounting base 34 for adhering to the combination of a toroidal coil 30 and core 32. Respective ends 30a, 30b of the toroidal coil extend through apertures in the PWB 33 upon which the toroidal coil and core combination are mounted. FIG. 3 illustrates another arrangement for mounting the combination of a toroidal coil 40 and core 42 to a PWB. In this approach, the toroidal coil/core combination is positioned in the upper, open portion of a potting tub 44. A potting compound (not shown) is deposited in the upper, open portion of the potting tub 44 for engaging the toroidal coil/core combination and maintaining it securely coupled to and positioned within the potting tub. The ends 40a, 40b of the toroidal coil 40 extend downward, beyond the potting tub 44 and are coupled to appropriate circuitry on the PWB upon which the potting tub is mounted.
Referring to FIG. 4, there is shown yet another arrangement for securely attaching a toroidal coil 48 and core 50 to a PWB, which is not shown in FIG. 4 for simplicity. In this approach, the toroidal coil/core combination is securely attached to a vertical support member 52 which, in turn, is mounted to a supporting PWB. The toroidal coil/core combination is typically attached to the vertical support member 52 by glue or a tie wrap or may be adapted for snap-in engagement with the vertical support member. Respective ends 48a, 48b of the toroidal coil 48 extend downward from the vertical support member 52 for coupling to circuitry on the PWB.
Another prior art approach is illustrated in FIG. 5 where a tie wrap 64 disposed about the circular periphery of the core 58 is securely attached at its respective ends to a PWB 60 by means of glue or epoxy cement 62. As shown in FIG. 5, the toroidal coil 56 is wound around the core 58 and outside of the tie wrap 64. FIG. 6 illustrates still another prior art approach for attaching a toroidal coil 66 and core 68 to a PWB 74. In the arrangement of FIG. 6, glue 72 is deposited on the PWB 74 and the toroidal winding/core combination is then placed in intimate contact with the glue. In the same manner as shown in the FIG. 5 embodiment, a tie wrap is then inserted through and around the toroidal coil/core combination and is inserted through a pair of apertures in the PWB 74 and is fastened thereto. The "non-based" mounting approach of FIG. 6 does not include the previously discussed contoured mounting base or potting tub. However, this mounting approach is time consuming and requires access to both sides of the PWB during installation.
All of the aforementioned prior art mounting approaches suffer from one or more shortcomings. For example, the gluing of the toroidal coil directly to the PWB surface increases the risk of adhesive contaminating the solder joints at respective ends of the coil Positioning of the adhesive in direct contact with the toroidal coil also makes PWB repair and toroidal coil replacement more difficult. The use of potting tubs or contoured base mounts requires an additional component to be inserted on the PWB in a labor intensive procedure involving either the insertion of threaded screws or one or more deposits of glue or epoxy cement. The incorporation of a vertical support member also requires the installation of an additional component as well as the separate step of attaching the toroidal coil/core combination to the vertical support member. Finally, the use of tie wraps involves manual manipulation in a labor intensive operation and requires access to both sides of the PWB.
The present invention overcomes the aforementioned limitations of the prior art by providing for the secure attachment of a toroidal coil/core combination to a PWB using a single mounting device which is easily inserted through and attached to a PWB while simultaneously engaging the toroidal coil/core combination and maintaining it in intimate contact with and securely attached to the PWB.